<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <div style="width: 100px ;height: 100px;"></div>
    <script>
        function getcolor(flag) {
            let arr = ['0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f']
            let str = '#'
            if (flag) {
                for (let i = 0; i < 6; i++) {
                    let ran = Math.floor(Math.random() * arr.length)
                    //str = str +arr[ran]
                    str += arr[ran]

                }
                return str
            } else {
                let r = Math.floor(Math.random() * 256)
                let g = Math.floor(Math.random() * 256)
                let b = Math.floor(Math.random() * 256)
                return `rgb(${r},${g},${b})`
            }
        }
        console.log(getcolor(true));
        console.log(getcolor(false));
        const divv = document.querySelector('div')
        divv.style.backgroundColor = getcolor(true)

    </script>
</body>

</html>